Method and Apparatus For Building Support Piers From One or Successive Lifts Formed In A Soil Matrix

ABSTRACT

A method and apparatus for forming a support aggregate pier having compacted aggregate lifts in a soil matrix, includes an elongate, hollow tube with a bulbous leading end bottom head element that is forced or lowered into the soil matrix. The hollow tube includes a mechanism for releasing aggregate from the lower head element of the tube as the tube is lifted in predetermined increments. The same hollow tube is then lowered or pushed in predetermined increments to vertically compact the released aggregate in thin aggregate lifts, while forcing a portion of the compacted aggregate transaxially into the soil matrix at the sidewalls of the cavity. The process may be repeated to form a series of compacted aggregate lifts comprising an aggregate pier or the process may include forming only a single lift for the aggregate pier while densifying adjacent matrix soils and imparting lateral stress in these soils.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation in part application of Ser. No.11/747,271 filed May 11, 2007 which is a continuation of Ser. No.10/728,405 filed Feb. 12, 2004 which is a utility application based uponprovisional application Ser. No. 60/513,755 filed Oct. 23, 2003, all ofwhich are incorporated herein by reference and for which priority isclaimed.

BACKGROUND OF THE INVENTION

In a principal aspect, the present invention relates to a method andapparatus for constructing a support pier comprised of one or morecompacted lifts of aggregate material. The apparatus enables formationor construction of a single or multi-lift pier within a soil matrixwhile simultaneously reinforcing the soil adjacent the pier. Theapparatus thus forms a cavity in the soil matrix by forcing a hollowtube device into the soil matrix followed by raising the tube device,releasing or injecting aggregate through the tube device into the cavitysection beneath the raised tube device and then for multi-lift piersdriving, pushing, lowering, and/or forcing, the tube device downward tocompact the released aggregate material while simultaneously forcing theaggregate material vertically downward and laterally outward into thesurrounding soil matrix.

In U.S. Pat. No. 5,249,892, incorporated herewith by reference, a methodand apparatus are disclosed for constructing short aggregate piers insitu. The process includes drilling a cavity in a soil matrix and thenintroducing and compacting successive layers or lifts of aggregatematerial in the cavity to form a pier that can provide support for astructure. Such piers are made by first drilling a hole or cavity in asoil matrix, then removing the drill, then placing a relatively small,discrete layer of aggregate in the cavity, and then ramming or tampingthe layer of aggregate in the cavity with a mechanical tamper. Themechanical tamper is typically removed after each layer is compacted,and additional aggregate is then placed in the cavity for forming thenext compacted layer or lift. The lifts or layers of aggregate, whichare compacted during the pier forming process, typically have a diameterof 2 to 3 feet and a vertical rise of about 12 inches.

This apparatus and process produce a stiff and effective stabilizingcolumn or pier useful for the support of a structure. However thismethod of pier construction has a limitation in terms of the depth atwhich the pier forming process can be accomplished economically, and thespeed with which the process can be conducted. Another limitation isthat in certain types of soils, especially sand soils, cave-ins occurduring the cavity drilling or forming process and may require the use ofa temporary casing such as a steel pipe casing. Use of a temporary steelcasing significantly slows pier production and therefore increases thecost of producing piers. Thus, typically the process described in U.S.Pat. No. 5,249,892 is limited to forming piers in limited types of soilat depths generally no greater than approximately 25 feet.

As a result, there has developed a need for a unique pier constructionprocess and associated special mechanical apparatus which can besuccessfully and economically utilized to form or construct aggregatepiers at greater depths, at greater speeds of installation, and in sandsor other soils that collapse and are unstable when drilled, without theneed for a temporary casing, yet having the attributes and benefitsassociated with the short aggregate pier method, apparatus, andconstruction disclosed in U.S. Pat. No. 5,249,892, as well as additionalbenefits.

SUMMARY OF THE INVENTION

Briefly, the present invention comprises a method for installation of apier formed from one or more layers or formed lifts of aggregatematerial, with or without additives, and includes the steps ofpositioning or pushing or forcing an elongate hollow tube having aspecial shaped bottom head element and unique tube configuration into asoil matrix, filling the hollow tube including the bottom head elementwith an aggregate material, releasing a predetermined volume ofaggregate material from the bottom head element as the hollow tube islifted a predetermined incremental distance in the cavity formed in thesoil matrix, and then imparting an axial, static vector force andoptional dynamic vector forces onto the hollow tube and its specialbottom head element to transfer energy via the lower end of the shapedbottom head element of the hollow tube to the top of the lift ofreleased aggregate material thereby vertically compacting the lift ofaggregate material and also, simultaneously forcing a portion of thereleased aggregate material laterally or transaxially into the sidewallsof the cavity. Lifting of the hollow tube having the special bottom headelement followed by pushing down with an applied axial or verticalstatic vector force and optional dynamic vector forces impacts theaggregate material which is not shielded by the hollow tube from thesidewalls of the cavity at the time of impaction, thereby densifying andvertically compacting the aggregate material as well as forcing aportion of the aggregate material laterally outward into the soil matrixdue to the shaped bottom of the bulbous bottom head element facilitatinglateral forces on and within the released aggregate material andtherefore imparting lateral stress on the adjacent soil matrix. Thereleased, compacted, and partially displaced aggregate material thusdefines a “lift” which generally has a lateral dimension or diametergreater than that of the cavity formed by the hollow tube and bulbousbottom head element resulting in a pier construction formed of one ormore compacted lifts of aggregate material.

The aggregate material is released from the special bottom head elementof the hollow tube as the bulbous bottom head element is lifted,preferably in predetermined incremental steps, first above the bottom ofthe cavity and then above the top portion of each of the successive pieraggregate lifts that has been formed in the cavity and the adjacent soilmatrix by the process. The aggregate material released from the hollowtube is compacted by the compacting forces delivered by the hollow tubeand special bottom head element after the hollow tube has been lifted toexpose a portion of the cavity while releasing aggregate material intothat exposed portion. The hollow tube and bulbous bottom head element isnext forced downward to vertically compact the aggregate and to push aportion of the aggregate laterally into the soil matrix. The aggregatematerial is thereby compacted and partially displaced in predetermined,sequential increments, or lifts. The process is continuously repeatedalong the length or depth of the cavity with the result that anaggregate pier or column of separately compacted lifts or layers isformed within the soil matrix. A vertically compacted aggregate pierhaving a length of fifty (50) feet or greater can be constructed in thismanner in a relatively short period of time without removal of thehollow tube and special bottom head element from the soil. The resultingvertically compacted aggregate pier also generally has a formed crosssectional dimension consistently greater than that of the hollow tube.

A number of types of aggregate material can be utilized in the practiceof the process including crushed stone of many types from quarries, orre-cycled, crushed concrete. Additives may include water, dry cement, orgrout such as water-cement sand-grout, fly-ash, hydrated lime orquicklime, or any other additive may be utilized which may improve theload capacity or engineering characteristics of the formed aggregatepier. Combinations of these materials may also be utilized in theprocess.

The hollow tube with the bulbous bottom head element may be positionedwithin the soil matrix by pushing and/or vertically vibrating orvertically ramming the hollow tube having the leading end, bulbousbottom head element into the soil with an applied axial or verticalvector static force and optionally, with accompanying dynamic vectorforces. The soil matrix, which is displaced by initial forcing, pushingand/or vibrating the hollow tube with the special bottom head element,is generally displaced and compacted laterally and vertically downwardinto the preexisting soil matrix. If a hard or dense layer of soil isencountered, the hard or dense layer may be penetrated by pre-drillingor pre-penetrating that layer to form a cavity or passage into which thehollow tube and special bottom head element may be placed and driven.

The hollow tube is typically constructed from a uniform diameter tubewith a bulbous bottom head element and may include an internal valvemechanism near or within the bottom head element or a valve mechanism atthe lower end of the head element, or it may not include an internalvalve closing and opening mechanism. The hollow tube is generallycylindrical with a constant, uniform, lesser diameter along an uppersection of the tube. The bulbous or larger external diameter lower endof the hollow tube (i.e. bulbous bottom head element) is integral withthe lesser diameter hollow tube or may be separately formed and attachedto the lower end of the lesser diameter hollow tube. That is, thebulbous bottom head element is also typically cylindrical, and has agreater external diameter or external cross sectional profile than theremainder of the hollow tube and is concentric about the center lineaxis of the hollow tube. The lead end of the bulbous bottom head elementis shaped to facilitate penetration into the soil matrix and to transmitdesired vector forces to the surrounding soil during penetration as wellas to the aggregate material subsequently released from the hollow tube.The transition from the lesser external diameter hollow tube section tothe special bottom head element may comprise a frustoconical shape.Similarly, the bottom of the head element may employ a frustoconical orconical shape to facilitate soil penetration and subsequent aggregatecompaction. The leading end of the bulbous bottom head element mayinclude a sacrificial cap member which is fixed to the bottom headelement while penetrating the soil matrix upon initial placement of thehollow tube into the soil matrix, to prevent soil from entering thehollow tube. The sacrificial cap may then be released or disengaged fromthe end of the hollow tube to reveal an end passage when as the hollowtube is first lifted so that aggregate material may be released throughthe hollow tube and may flow into the cavity which results from liftingthe hollow tube.

Alternatively, or in addition, the leading end of the bulbous bottomhead element may include an internal mechanical valve that is closedduring initial penetration of the soil matrix by the hollow tube andbulbous bottom head element, but which may be opened during lifting torelease aggregate material. Other types of leading end valve mechanismsand shapes may be utilized to facilitate initial matrix soilpenetration, prevent soil entrance into the hollow tube, permit releaseof aggregate material when the hollow tube is lifted, and to transmitvector forces in combination with the leading end of the special bottomhead element to compact the successive aggregate lifts.

Further, the apparatus may include means for positioning one or morevertical uplift members within the formed pier for subsequent use as avertical uplift anchor force resistance member, as well as for atell-tale member within the formed pier for measuring the movement ofthe bottom of the formed pier upon loading, such as during load testing.Such ancillary features or means may be introduced through the interiorof the hollow tube during formation of the pier.

Alternatively, uplift anchor rods or a tell-tale rod or rods may beplaced on the outside of the hollow tube and the bulbous bottom headelement. Such rods would run longitudinally along the length of thehollow tube and head element and thus be positioned at the side of thecavity formed thereby. One, or two or more rods may be placed in such amanner. The rods placed on the outside of the hollow tube and headelement may be employed alone or in combination with such rods initiallypositioned on the inside of the hollow tube.

As yet another feature of the invention, vibration dampers may beemployed in combination with a hopper that feeds aggregate or othermaterial into the hollow tube. Thus, two or more dampers may be used andthus, employed in combination with the driving mechanism.

In another aspect of the invention, the diameter of the hollow tubealong its longitudinal length between the hopper or top end of thehollow tube and the bulbous bottom head element may be varied. Thelargest diameter hollow tube section may be positioned at the top of thehollow tube, with progressively smaller diameter sections below thelargest diameter section, the smallest of which is joined to the bottomhead element. This arrangement can effect reduction in total weight ofthe hollow tube, while increasing the strength in those portions of thehollow tube where greater strength is required. The hollow tube may beassembled in multiple sections which are bolted, welded or otherwisefastened together. The outer configuration of adjacent sections may alsobe varied, for example, they may have various geometrical crosssectional shapes such as circular, elliptical, hexagonal, etc. Thesections may be pre-assembled or assembled by connecting them seriatimduring soil penetration.

In the practice of the method of the invention, it may be advantageousto utilize crushed stone which has angular facets or faces rather thanrounded or river stone which is more commonly used with other soilimprovement methods. The ability to use crushed stone in the practice ofthe method enables the use of a material not commonly employed forbuilding such piers and, as such, provides the capability to construct apier having certain practical advantages such as a higher density and agreater stiffness. Nonetheless, rounded or river stone may also be used.Combinations of such stone including crushed stone and rounded or riverstone may also be used.

As another feature of the invention, the hollow tube and bulbous bottomhead element may be appropriately guided in movement into the soilmatrix by means of an alignment guide. The alignment guide provides anadditional function of preventing the hollow tube and special bottomhead element from displacing laterally (“kicking out”) during initialpenetration into the soil matrix. One example of a special alignmentguide is a toroidal guide member encircling the hollow tube and fastenedto the drive machine to provide for guidance thereof for the hollow tubeand bulbous bottom head element. Other forms of special alignment guidescan be utilized and more than one alignment guide may be utilized.

As yet another feature, the hollow tube and bulbous bottom head elementmay be forced or driven into a soil matrix by means of a vibratoryhammer which is fastened thereto by means of a lock plate construction.The lock plate is held in position by bolts or rods which are retainedby special lock washers, for example, the special lock washers havingthe commercial name “Northlock Washers”. This arrangement reduces theelectricity created between the driving apparatus and the hollow tubewith bulbous bottom head element.

The typical exterior diameter of a circular cross section embodiment ofthe special bottom head element is in the range of about 14 inches.Other typical sizes in terms of the diameter of the head element includea head element having a diameter of anywhere from 12 to 16 inches andthe range of the practicable diameters of a head element may be fromabout 10 to about 20 inches. This differs from other tubular apparatusfor soil improvement which typically are larger, from 24 to 36 inches indiameter. The shape of the head element in cross section is typicallycylindrical, although other shapes may be utilized to provide therelative bulbous shape of the bulbous bottom head element whencontrasted with the cross sectional area of the hollow tube sectionattached thereto.

A sensor device may be attached to the bulbous bottom head element tomeasure the vertical force over time as encountered by the bulbousbottom head element during the vertical compaction and lateraldisplacement of aggregate process. The sensor device enables measurementof the vertical force and the duration of vertical force being placedthereon. The sensor device can be attached to the bulbous bottom headelement, for example, just above the lower shaped portion thereof toprovide axial and transaxial readings.

As another feature, the apparatus of the invention may be used incombination with aggregate, with cementations grout in combination withaggregate, or with concrete, as well as other pier forming materials.

As another feature, the apparatus and method of the invention may beutilized in stiff, very stiff, medium dense or hard soils. In certaincircumstances, one may pre-drill at least in part the soil at a pierlocation. Alternatively, it is possible to pre-penetrate the soil at apier location with a special designed penetration head element fastenedto a shaft. The cross sectional area of the shaft is typically less thanthe maximum cross sectional area of the penetration head element. Themaximum diameter of the penetration head element is typically less thanthe diameter of the bulbous bottom head element attached to the elongatehollow tube. A conical penetration head on a shaft is an effective shapefor the special designed penetration head element, although otherconfigurations may be used. The operation of the pre-penetration step isprior to and typically separate from the steps of installing the pier bymeans of the hollow tube and bulbous bottom head element.

As another feature of the invention, aggregate piers made in accord withthe apparatus and method of the invention may be installed at a depthbeneath a soil surface. The aggregate pier may then serve as a base orsupport for an alternative type of pier construction. Thus, two or moredifferent types of pier segments, one of which is the system describedherein, may be joined or coupled or stacked to form a single pier.

The discharge opening at the extreme distal end of the bulbous bottomhead element may vary in size. Typically, since the bottom head elementis utilized to discharge aggregate or other similar material from anopening, then a portion of the extreme distal end of the bulbous bottomhead element will comprise a generally horizontal structure coupled witha conical or generally conical surface. The bottom opening willtypically comprise less than fifty percent of the surface area of thegenerally horizontal portion or section and the generally conicalsurface portion. The horizontal bottom portion and the generally conicalportion impart forces directly onto aggregate released or dischargedfrom the bottom opening.

Thus, it is an object of this invention to provide a hollow tubeapparatus with a special design, larger effective diameter than thehollow tube, bulbous bottom head element useful to create a compactedaggregate pier, with or without additives, that extend to a greaterdepth and to provide an improved method for creating a pier whichextends to a greater depth than typically enabled or practiced by known,existing short aggregate pier technology.

Yet another object of the invention is to provide an improved method andapparatus for forming a pier of compacted aggregate material that doesnot require the use of temporary steel casing during the pier formationprocess, particularly in soils susceptible to caving in such as sandysoils and soils below the ground water table.

Yet another object of the invention is to provide an improved method andapparatus for forming a pier of compacted aggregate material that mayinclude a multiplicity of optional additives, including a mix ofaggregate, the addition of water, the addition of dry cement, theaddition of cementitious grout, the addition of water-cement-sand, theaddition of fly-ash, the addition of hydrated lime or quicklime, and theaddition of other types of additives, including the use of concrete, toimprove the engineering properties of the matrix soil, of the aggregatematerials and of the formed pier.

Yet a further object of the invention is to provide an aggregatematerial pier construction which is capable of being installed in manytypes of soil and which is further capable of being formed at greaterdepths and at greater speeds of construction than known prior aggregatepier constructions.

Yet a further object of the invention is to provide an improved methodand apparatus for forming a pier of compacted aggregate material withina softened or loosened aggregate pier previously formed by differentpier construction process and with different apparatus than thatdescribed herein in order to stabilize and stiffen the previously formedpier.

Another object of the invention is to provide a pier forming apparatususeful for quickly and efficiently constructing compacted multi-liftaggregate piers and/or aggregate piers comprised of as few as a singlelift.

These and other objects, advantages and features of the invention willbe set forth in the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description which follows, reference will be made to thedrawing comprised of the following figures:

FIG. 1 is a schematic view of a hollow tube with a special bottom headelement being pushed, forced or driven into soil by a vertical, staticvector force and optional dynamic forces;

FIG. 2 is a schematic view of a subsequent step from FIG. 1 whereinaggregate material is placed into a hopper and fed into the hollow tube.Hopper may also be detached from the hollow tube and placed on theground rather than on top of the hollow tube;

FIG. 3 is a cross sectional view of a hopper that has double two or moreisolation dampers and may be used in combination with the hollow tube;

FIG. 3A is a sectional, isometric view of the hopper and hollow tube ofFIG. 3;

FIG. 3B is an isometric view of the hopper and hollow tube of FIG. 3;

FIG. 4 is a cross sectional schematic view of a hollow tube having aninternal pinch or check valve;

FIG. 5 is a schematic view depicting the step of optional introductionof water, cementatious grout or other additive material into the hollowtube with recirculation provided to a water or grout reservoir. Additivematerials may also be introduced directly into the hollow tube;

FIG. 6 is a schematic view depicting a step subsequent to the step ofFIG. 2 wherein the hollow tube with its bulbous bottom head element arelifted a predetermined distance to temporarily expose a hollow cavityportion in the soil matrix to allow aggregate to quickly fill theexposed hollow cavity portion;

FIG. 7 is a schematic view of the process step subsequent to FIG. 6wherein a bottom valve in the bottom portion of the hollow tube isopened releasing aggregate into an unshielded, hollow cavity section;

FIGS. 8A and 8B are schematic cross sectional views of an alternative tothe device and step represented or illustrated in FIG. 7 wherein thebulbous bottom head element of the hollow tube includes a sacrificialcap which is released into the bottom of a formed cavity when the hollowtube and special bottom head element are raised a predetermineddistance, as shown in FIG. 8B;

FIG. 8C is a sectional view of the sacrificial cap of FIG. 8B takenalong the line 8C-8C in FIG. 8B;

FIG. 9 is a schematic view wherein the hollow tube and its associatedspecial bottom head element provide a vertical, static vector force withoptional dynamic forces to move the hollow tube and bulbous bottom headelement downward a predetermined distance by impacting and compactingthe aggregate material released from the hollow tube and by pushing aportion of the aggregate material laterally into the soil matrix;

FIG. 10 is a schematic view of the hollow tube and its special bottomhead element being lifted a predetermined distance to form a secondlift;

FIG. 11 is a schematic view of the hollow tube and bulbous bottom headelement operating to provide a vertical vector force to move the hollowtube and bulbous bottom head element downward a predetermined distanceto form the second compacted lift on the top of a first compacted lift;

FIG. 12 is a schematic view of the hollow tube with an optionalreinforcing steel rod element or tell-tale element attached to a platefor installation inside of a formed aggregate pier;

FIG. 13 is a schematic view of the hollow tube wherein optional water orwater-cement-sand grout, or other additive is combined with aggregate inthe hollow tube;

FIG. 14 is a vertical cross sectional view of the special bottom headelement with a trap door-type bottom valve;

FIG. 15 is a cross sectional view of the bulbous bottom head element ofFIG. 14 taken along the line 15-15;

FIG. 15A is a cross sectional view of a portion of an alternativebulbous bottom head element of the type depicted in FIG. 14;

FIG. 16 is a cross sectional view of the special bottom head elementincluding a sacrificial cap at the lower end similar to FIG. 8A;

FIG. 17 is a cross sectional view of the special bottom head elementwith an optional uplift anchor member or tell-tale member attached to aplate;

FIG. 18 is a cross sectional view of a partially formed multiple liftaggregate pier formed by the hollow tube and special bottom head elementand method of the invention;

FIG. 19 is a cross sectional view of a completely formed multiple liftaggregate pier formed by hollow tube and special bottom head element andmethod of the invention;

FIG. 20 is a cross sectional view of a formed, multiple lift aggregatepier with an optional reinforcing steel rod having an attached platewhich enables the formed pier to comprise an uplift anchor pier or toinclude a tell-tale element for subsequent load testing;

FIG. 21 is a cross sectional view of formed aggregate pier beingpreloaded or having an indicator modulus load test being performed onthe completed pier;

FIG. 22 is a graph illustrating comparative load test plots of thepresent invention compared with a drilled concrete pile in the same soilmatrix formation;

FIG. 23 is a schematic, cross sectional view of a method of use of theapparatus of the invention to form a single lift aggregate pier or anaggregate pier wherein a single lift or an extended lift is first formedto fill the cavity with aggregate and then an optional second step maybe performed of re-penetrating into the single lift or extended lift tomake subsequent thin lifts;

FIG. 24 is a schematic cross sectional view of continuation of themethod illustrated by FIG. 23;

FIG. 25 is a schematic cross sectional view of further continuation ofthe step depicted in FIG. 24;

FIG. 26 is a schematic cross sectional view of the further continuationof the method illustrated by FIGS. 22-24;

FIG. 27 is a diagrammatic view illustrating the incorporation of two ormore uplift or tell-tale rods external to the hollow tube and attachedbottom plate or sacrificial cap;

FIG. 27A is a lateral side view of the construction of FIG. 27;

FIG. 27B is a bottom plan view of the construction of FIG. 27;

FIG. 28 is a diagrammatic view illustrating apparatus incorporatingdifferent cross sectional area sections of a hollow elongate tube incombination with a bulbous bottom head element;

FIG. 29 is a diagrammatic view of an aggregate pier which incorporatesuplift anchors;

FIG. 30 is a diagrammatic view of an aggregate pier made in accord withthe invention which incorporates tell-tale rods utilized for the conductof load tests;

FIG. 30A is a detail showing tell-tale details for aggregate pier.

FIG. 31 is a diagrammatic view of an embodiment of the inventionapparatus for aligning the hollow tube and bulbous bottom head upon forinsertion into a soil matrix;

FIG. 32 is a diagrammatic view of a bulbous bottom head elementincorporating a sensor device for measuring force or pressure over timeduring the making of an aggregate pier;

FIG. 33 is an exploded diagrammatic view of apparatus for attachment ofa vibratory hammer to a hollow tube in order to effect positioning ofthe hollow tube and bulbous bottom head element into a soil matrix;

FIG. 34 is a diagrammatic view of a soil matrix pre-penetration devicewhich may be used in combination with apparatus comprising an embodimentof the invention;

FIG. 35 is a diagrammatic view of a pier comprised of a composite ofpier sections made in accord with a method of the invention incombination with other methods to result in a new combination;

FIG. 36 is a bottom end view of a bulbous bottom head element depictingthe orifice or opening at the extreme distal end thereof for the passageof aggregate and/or other material;

FIG. 37 is a diagrammatic drawing of an alternate constructioncomprising a telescoping hollow tube; and

FIG. 38 is a further diagrammatic drawing of the embodiment of FIG. 37.

DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

General Construction:

FIGS. 1, 2, 5, 6, 7, 9, 10, 11, 12, 13, 18, 19, 20 and 23-26 illustratethe general overall method of construction of the pier forming device ormechanism and various as well as alternative sequential steps in theperformance of the method of the invention that produce the resultantaggregate pier construction. Referring to FIG. 1, the method isapplicable to placement of piers in a soil matrix which requiresreinforcement for the soil to become stiffer and/or stronger. A widevariety of soils may require the practice of this invention including,in particular, sandy and clay soils. With the invention, it is possibleto construct piers comprised of one or more lifts, utilizing aggregatematerials and optionally utilizing aggregate materials with additivematerials such as water, cement, sand or grout. The resulting piers havegreater stiffness and strength than many prior art aggregate piers, caneconomically be extended to or built to greater depths than many priorart aggregate piers, can be formed without use of temporary steel casingunlike many prior art aggregate piers, can be installed faster than manyprior art aggregate piers, can be installed using less aggregatematerials per foot of pier length than many prior art aggregate piers,and can be installed without causing soil matrix spoils from beingdischarged or accumulating at the ground surface in the vicinity of thetop of pier.

As a first step of the method, a hollow tube or hollow shaft 30 having alongitudinal axis 35 including or with a special bottom head element 32,is pushed by a static, axial vector force driving apparatus 37 in FIG. 3and optionally vertically (axially) vibrated or rammed or both, withdynamic vector forces, into a soil matrix 36. The portion of soil matrix36, that comprises the volume of material displaced by pushing a lengthof the hollow tube 30 including the bulbous bottom head element 32, isforced primarily laterally thereby compacting the adjacent soil matrix36. As shown in FIG. 1, the hollow tube 30 may comprise a cylindricalsteel tube 30 having a longitudinal axis 35 and an external diameter inthe range of 6 to 14 inches, for example. In the event that a layer ofhard or dense soil prevents pushing of the hollow tube 30 and specialbottom head element 32 into the soil matrix 36, such hard or dense layermay be pre-drilled, or pre-penetrated, and the pushing process may thencontinue utilizing the driving apparatus 37.

Typically, the hollow tube 30 has a uniform cylindrical external shape,although other shapes may be utilized. Though the external diameter ofthe hollow tube 30 is typically 6 to 14 inches, other diameters may beutilized in the practice of the invention. Also, typically, the hollowtube 30 will be extended or pushed into the soil matrix 36 to theultimate depth of the aggregate pier, for example, up to 50 feet ormore. The hollow tube 30 will normally fasten to an upper end driveextension 42 which may be gripped by a drive apparatus or mechanism 37to push and optionally vibrate or ram, the hollow tube 30 into the soilmatrix 36. Alternately, as shown in FIG. 33, the hollow tube 30 may befastened to a base plate 558 and from the base plate to the driveapparatus 556.

FIGS. 3, 3A and 3B illustrate a feature that may be associated with thehopper 34 when the hopper is located at the top of the hollow tube 30.Double isolation dampers 46, 48 are affixed to the upper and lower sidesof the hopper 34 to reduce the vibration buildup of the hopper 34 andthereby provide a hopper assembly with greater structural integrity. Anextension 42 is affixed to hollow tube 30 to impart the static anddynamic forces on the tube 30. Extension 42 is isolated from hopper 34and thus is slidable relative to dampers 46, 48.

The hopper 34, which contains a reservoir 43 for aggregate materials,when located at the top of the hollow tube 30, will typically beisolated by the isolation dampers 46, 48 from extension 42. Thevibrating or ramming device 37 which is fastened to extension 42 may besupported from a cable or excavator arm or crane. The weight of thehopper 34, ramming or vibrating device 37 (with optional additionalweight) and the hollow tube 30 may be sufficient in some matrix soilconditions to provide a static force vector without requiring use of aseparate static force drive mechanism. The static force vector mayoptionally be augmented by a vertically vibrating and/or ramming dynamicforce mechanism. Also, the hopper 34 may be separate from the hollowtube 30 and extension 42. For example, a separate hopper not mounted onthe top of the hollow tube 30 (not shown) may feed aggregate or othermaterial into the hollow tube 30 along the side of the tube.

FIG. 3(c) illustrates the manner of incorporating a copper 34 incombination with a tube for feeding aggregate or other material into apassage formed in the soil matrix. Specifically damper mechanisms 46 and48 are attached respectively to the hopper 34 and to the feed tube 42.The attachment is effected through an elastic connector 46 and 48 whicheffectively dampens the forces, particularly laboratory forces that maybe imparted to the vertical feed tube 42.

FIG. 4 illustrates an optional feature of the hollow tube 30. Arestrictor, pinch valve, check valve or other type of valve mechanism 38may be installed within the hollow tube 30 or in the special bottom headelement or lower end section 32 of the hollow tube 30 to partially ortotally close off the internal passageway of the hollow tube 30 and stopor control the flow or movement of aggregate materials 44 and optionaladditive materials. This valve 48 may be mechanically or hydraulicallyopened, partially opened or closed in order to control movement ofaggregate materials 44 through the hollow tube 30. It may also operateby gravity in the manner of a check valve which opens when raised andcloses when lowered onto the aggregate material 44.

FIG. 14 illustrates a construction of the bulbous bottom head element orsection 32. The bulbous bottom head element 32 is cylindrical, althoughother shapes may be utilized. The external diameter of the specialbottom head element 32 is greater than the nominal external diameter ofthe upper section 33 of the hollow tube 30 and is typically 12 to 18inches, although other diameters and/or cross sectional profiles may beutilized in the practice of the invention. Thus, the head element 32will have cross sectional dimensions or area greater than that of hollowtube 30 immediately adjacent thereto.

FIGS. 14, 15 and 15A illustrate an embodiment of the invention having avalve mechanism incorporated in the bulbous bottom head element 32. Thebulbous bottom head element 32 has a frustoconical bottom section orother shaped, bottom portion 50 with an aggregate material 44 dischargeopening 52 that opens and closes as a valve plate 54 exposes or coversthe opening 52. The valve plate 54 is mounted on a rod 56 that slides ina hub 59 held in position by radial struts 58 attached to the insidepassage walls of the bulbous bottom head element 32 of the hollow tube30. The plate 54 slides to a closed position when the hollow tube 30 isforced downward into the soil matrix 36 and slides to an open positionwhen hollow tube 30 is raised, thus allowing aggregate material 44 toflow. The opening of valve 54 is controlled or limited by rod 56 whichhas a head 56 a that limits sliding movement of rod 56. The hollow tube30 may thus be driven to a desired depth 81 (FIG. 6) with opening 52closed by plate 54. Then as the hollow tube 30 is raised (for example,the distance 91 in FIG. 10), the plate 54 extends or moves downwardlydue to gravity so that aggregate material 44 will flow through opening52 into the cavity formed due to the raising of the hollow tube 30.Thereafter, the tube 30 is impacted or driven downwardly closing valveplate 54 and compacting the released material to form a compacted lift72. In the embodiment of FIGS. 14, 15, 15A the valve plate 54 moves inresponse to gravity. However, rod 56 may alternatively be replaced orassisted in movement by a fluid drive, mechanical or electricalmechanism. Alternatively, as described hereinafter, the plate 54 may bereplaced by a sacrificial cap 64 or by the bottom plate of an upliftanchor or a tell-tale mechanism 70 as described hereinafter. Also, thecheck valve 38 in FIG. 4 may be utilized in place of the valve mechanismdepicted in FIGS. 14, 15, 15A.

Typically, the internal diameter of the hollow tube 30 and head element32 are uniform or equal, though the external diameter of the bulbousbottom head element 32 is greater than that of hollow tube 30.Alternatively, when a valve mechanism 54 is utilized, the internaldiameter of the head element 32 may be greater than the internaldiameter of the hollow tube 30. Bulbous bottom head element 32 may beintegral with hollow tube 30 or formed separately and bolted or weldedonto hollow tube 30. Typically, the inside diameter of the hollow tube30 is between 6 to 10 inches and the external diameter of the specialbottom head element 32 is about typically 12 to 18 inches. The openingdiameter 53 in FIG. 14 at the extreme lower end or leading end of thespecial bottom head element 32 may be equal to or less than the internaldiameter of the head element 32. For example, referring to FIG. 14, thehead element 32 may have an internal diameter of 12 inches and theopening diameter 53 may be 6 to 10 inches, while in FIG. 16, with thesacrificial cap embodiment described hereinafter, the discharge openingof head element 32 has the same diameter as the internal diameter of thehead element 32 and hollow tube 30.

Also the plate or valve 54 may be configured to facilitate closure whenthe hollow tube 30 is pushed downward into the soil matrix 36 or againstaggregate material 44 in the formed cavity. For example, the diameter ofmember 54 may exceed that of opening 52 as shown in FIG. 14 or the edge55 of the valve member may be beveled as depicted in FIG. 15A to engagebeveled edge 59 of opening 52. Then when applying a static or otherdownward force to the hollow tube 30, the valve plate 54 will be held ina closed position relative to opening 52.

The lower bulbous bottom head element 32 of hollow tube 30 typically hasa length in the range of one to three times its diameter or maximumlateral dimension. The bulbous bottom head element 32 provides enhancedlateral compaction forces on the soil matrix 36 as tube 30 penetrates oris forced into the soil and thus renders easier the subsequent passageof the lesser diameter section 33 of the hollow tube 30. Thefrustoconical or inclined leading and trailing edges 50, 63 of the headelement 32 facilitate lowering or driving penetration and lateralcompaction of the soil 36 because of their profile design. The trailinginclined section or edge 63 in FIG. 14 facilitates the raising of thehollow tube 30 and head element 32 and lateral compaction of soil matrix36 during the raising step of the method. Again, the shape or inclinedconfiguration of bulbous bottom head element 32 enables this to occur.Typically the leading and trailing edges 50, 63 form a 45°±15° anglewith the longitudinal axis 35 of the hollow tube 30.

FIG. 5 illustrates another feature of the hollow tube 30. Inlet port 60and outlet port 62 are provided at the lower portion of the elevatedhopper 34 or the upper end of hollow tube 30 to allow addition of wateror of grout, such as water-cement-sand grout, as an additive to theaggregate for special pier constructions. A purpose of the outlet port62 is to maintain the water or additive level where it will be effectiveto facilitate flow of aggregate and also to allow recirculation of thegrout from a reservoir back into the reservoir to facilitate mixing andto keep the water head or grout head (pressure) relatively constant. Theinlet port 60 and outlet port 62 may lead directly into the hopper 34 ordirectly into the hollow tube 30 (see FIG. 13), or may connect withseparate channels or conduits to the bulbous bottom head element 32.Grout discharge openings 31 may be provided through hollow tube 30 abovebulbous bottom head element 32 as shown in FIG. 2 to supplementdischarge of grout into the annular space about hollow tube 30 andprevent cavity fill in by soil from the matrix 36.

FIGS. 8A, 8B, 8C and 16 illustrate another alternate feature of thebulbous bottom head element 32. A sacrificial cap 64 may be utilized inlieu of the bottom or lower end sliding valve 54 to protect the bulbousbottom head element 32 from clogging when the bulbous bottom headelement 32 is pushed down through soil matrix 36. The cap 64 may beconfigured in any of a number of ways. For example, it may be flat,pointed or beveled. It may be arcuate. When beveled, it may form anangle of 45°±25° with respect to horizontal axis 35. Cap 64 may includea number of outwardly biased legs 87 positioned to fit in the centralopening 89 of the bulbous bottom head element 32 and hold cap 64 inplace until hollow tube 30 is first raised and aggregate 44 caused toflow out the opening 52 into an exposed cavity section.

FIG. 17 illustrates another alternate feature of the bottom head element32. The sliding plate 54 and rod 68 for support of plate 54 may includea passage or axial tube 57 that allows the placement of a reinforcingelement or rod 68 attached to a bottom plate 70. The rod 68 and plate 70will be released at the bottom of a formed cavity and used to provide anuplift anchor member or a tell-tale member for measuring bottom movementof a pier during a load test. The sliding rod 68 attached to a bottomplate 70 may be substituted for the sacrificial cap 64 closing theopening of the bulbous bottom head element 32 during pushing into thesoil matrix 36, and perform as a platform for the uplift anchor memberor tell-tale member being installed. The bottom valve plate 54 may thusbe omitted or may be kept in place while the uplift anchor or tell-taleelements are being utilized. FIG. 20 illustrates the uplift anchor 68,70 or tell-tale in place upon the forming of a pier by the inventionwherein the plate or valve 54 is omitted.

Method of Operation:

FIG. 1 illustrates the typical first step of the operation of thedescribed device or apparatus. The hollow tube 30 with bulbous bottomhead element 32 and attached upper extension 42 and connected hopperassembly 34, are pushed with a vertical or axial static vector force,typically augmented by dynamic vector forces, into the soil matrix 36 bydrive apparatus 37 or by the weight of the component parts. In practice,utilizing a tube 30 with special bottom head element 32 having thedimensions and configuration described, a vector force of 5 to 20 tonsapplied thereto is typical throughout. FIG. 2 illustrates placing ofaggregate 44 into the hopper 34 when the hollow tube 30 and attachmentsreach the planned depth 81 of pier into the soil matrix 36. FIG. 6illustrates subsequent upward or lifting movement of the hollow tube 30by a predetermined lifting distance 91, typically 24 to 48 inches toreveal a portion of unshielded cavity 102 below the lower section headelement 32 in the soil matrix 36.

FIG. 7 illustrates opening of the bottom valve 54 to allow aggregate 44and optional additives to fill the space or portion 85 of cavity 102below the bulbous bottom head element 32 while the hollow tube 30 andattachments are being raised. The valve 54 may open as the hollow tube30 is lifted due to weight of aggregate 44 on the top side of valve 54.Alternatively, valve 54 may be actuated by a hydraulic mechanism forexample, or the hollow tube 30 may be raised and aggregate then added toflow through valve opening 53 by operation of valve 54. Alternatively,internal valve 38 may be opened during lifting or after lifting.Alternatively, if there is no valve 54, the sacrificial cap 64 will bereleased from the end of the head element 32, generally by force exertedby the weight of aggregate material 44 directed through the hollow tube30 when the bulbous bottom head element 32 is raised a predetermineddistance from the bottom 81 of the formed pier cavity 102.

FIG. 9 illustrates the subsequent pushing downward of the hollow tube 30and attachments and closing of the bottom valve 54 to compact theaggregate 44 in the cavity portion 85 thereby forcing the aggregate 44and optional additives laterally into the soil matrix 36 as well asvertically downward. The predetermined movement distance for pushingdownward is typically equal to the lifting distance 91 minus one foot,in order to produce a completed lift 72 thickness of one foot followingthe predetermined lifting distance 91 of hollow tube 30. The designedthickness of lift 72 may be different than one foot depending on thespecific formed aggregate pier requirements and the engineeringcharacteristics of the soil matrix 36 and aggregate 44. Compacting theaggregate material 44 released into the vacated, unshielded cavityportion 85 in FIG. 7 to effect lateral movement of the aggregatematerial 44 horizontally as well as compaction of the aggregate materialvertically is important in the practice of the invention.

FIG. 10 illustrates the next or second lift formation effected bylifting of the hollow tube 30 and attachments another predetermineddistance 91A, typically 24 to 48 inches to allow opening of the bottomvalve 54 (in the event of utilization of the embodiment using valve 54)and passage or movement of aggregate 44 and optional additives into theportion of the cavity 85A that has been opened or exposed by raisingtube 30.

Raising of the hollow tube in the range of two (2) to four (4) feet istypical followed by lowering (as described below) to form an aggregatepier lift 72, having a one (1) foot vertical dimension is typical forpier forming materials as described herein. The axial dimension of thelift 72 may thus be in the range of ¾ to ⅕ of the distance 91 the hollowtube 30 is raised. However, the embodiment depicted in FIGS. 23-26constitutes an alternate compaction protocol.

FIG. 11 illustrates pushing down of the hollow tube 30 and attachmentsand closing of the bottom valve 54 to compact the aggregate 44 in thenewly exposed, unshielded cavity portion 85A of FIG. 10 and forcing ofaggregate 44 and optional additives laterally into the soil matrix 36.The distance of pushing will be equal to the distance of lifting minusthe designed lift thickness. When the sacrificial cap 64 method isutilized, the bottom opening 50 may remain open while compacting theaggregate 44.

FIG. 18 illustrates an aggregate pier partially formed by the processdescribed wherein multiple lifts 72 have been formed sequentially bycompaction and the hollow tube 30 is rising as aggregate 44 is fillingcavity portion 85X. FIG. 19 illustrates a completely formed aggregatepier 76 by the process described. FIG. 20 illustrates a formed pier 76with uplift anchor member 68, 70 or tell-tale member installed. FIG. 21illustrates an optional preloading step on a formed aggregate pier 76 byplacement of a weight 75, for example, on the formed pier and anoptional modulus indicator test being performed on the formed aggregatepier 76 comprised of multiple compacted lifts 78.

FIGS. 23 through 26 illustrate an alternative protocol for the formationof a pier using the described apparatus. The hollow tube 30 is initiallyforced or driven into a soil matrix 36 to a desired depth 100. Theextreme bottom end of the head element 32 includes a valve mechanism 54,sacrificial cap 64 or the like. Forcing the hollow tube 30 verticallydownward in the soil forms a cavity 102 (FIG. 23). Assuming the specialbottom head element 32 is generally cylindrical, cavity 102 is generallycylindrical, and may or may not maintain the full diameter configurationassociated with the shape and diameter of special bottom head element32.

Upon reaching the desired penetration into the matrix soil 36 (FIG. 23)and having displaced and densified the matrix soils that previouslyexisted within the formed cavity, the hollow tube 30 is raised to thetop of the formed cavity or to the top of the planned aggregate pier(FIG. 24) in a single lift. As it is raised, aggregate material 44 andoptional additive materials are discharged below the bottom end of thespecial bottom head element 32.

Optionally, additive materials are discharged into the annular space 104defined between the upper section 33 of hollow tube 30 and the interiorwalls of the formed cavity 102. The additive materials may flow throughancillary lateral passages 108 or supplemental conduits 110 in thehollow tube 30. As the hollow tube 30 is raised, the cavity 102 isfilled with aggregate and optionally, additive materials. Also, additivematerials in the annular space 104 may be forced outwardly into the soilmatrix 36 by and due to the configuration of the bulbous bottom headelement 32 as it is raised.

The hollow tube 30 is thus typically raised substantially the fulllength of the initially formed cavity 102 and then, as depicted by FIG.25, again may be forced downward causing the aggregate material in thecavity 102 to be compacted and a portion of the aggregate materials tobe forced laterally into the soil matrix 36 (FIG. 25). The extent ofdownward movement of the hollow tube 30 is dependent on various factorsincluding the size and shape of the cavity 102, the composition and mixof aggregate materials and additives, the forces imparted on the hollowtube 30, and the characteristics of the soil matrix 36. Typically, thedownward movement is continued until the lower end or bottom of thespecial bottom head element 32 is at or close to the bottom 81 of thepreviously formed cavity 102 or until essential refusal of downwardmovement occurs.

After completion of the second downward movement, the hollow tube 30 israised typically the full length of the cavity 102, again dischargingaggregate and optionally additive materials during the raising, andagain filling, the newly created cavity 102A (FIG. 26). The cycle offully lowering and fully raising is completed at least two times andoptionally three or more times, to force more aggregate 44 andoptionally additive materials, laterally into the matrix soil 36.Further, the cycling may be adjusted in various patterns such as fullyraising and lowering followed by fully raising and partially lowering,or partially raising and fully lowering, and combinations thereof.Alternately, after one of more full cycles of raising of the hollow tube30 with discharging of aggregate and optionally additive materials, thesubsequent operation can be the same or similar to a typical aggregatepier forming sequence as described previously, where each lift is formedby raising and lowering a predetermined distance.

Alternatively, after completion of a single lift, the resultingaggregate pier with or without optional additive materials, furthersteps of re-entry of hollow tube 30 and bulbous bottom head element 32into the formed single lift aggregate pier, may be eliminated. In otherwords, the apparatus may be used to form a single elongate pier withinthe soil matrix extending the vertical length of soil penetration. Thesingle lift aggregate pier with densified adjacent matrix soils may beeffective without further strengthening or stiffening. One situation inwhich a single lift aggregate pier will typically be effective is inliquefaction mitigate during seismic events when the matrix soils areliquefiable.

Summary Considerations:

Water or grout or other liquid may be utilized to facilitate flow andfeeding of aggregate material 44 through hollow tube 30. The water maybe fed directly into the hollow tube 30 or through the hopper 34. It maybe under pressure or a head may be provided by using the hopper 34 as areservoir. The water, grout or other liquid thus enables efficient flowof aggregate, particularly in the small diameter hollow tube 30, i.e. 5to 10 inches tube 30 diameter. Typically the size of the tube 30internal passage and/or discharge opening is at least 4.0 times themaximum aggregate size for all the described embodiments. With each lift72 being about 12 inches in vertical height and the internal diameter oftube 30 being about 6 to 10 inches, use of water as a lubricant isespecially desirable.

It is noted that the diameter of the cavity 102 formed in the matrixsoil 36 is relatively less than many alternative pier formingtechniques. The method of utilizing a relatively small diameter cavity102 or a small dimension opening into the soil matrix 36, enablesforcing or driving a tube 30 to a significant depth and subsequentformation of a pier having horizontal dimensions measurably greater thanthe external dimensions of the tube 30. Utilization of aggregate 44 withor without additives including fluid materials, to form one or morelifts by compaction and horizontal displacement is thus enabled by thehollow tube 30 and special bottom head element 32 as described. Lifts 72are compacted vertically and aggregate 44 forced transaxially with theresult of a highly coherent pier construction and production of astiffer and stronger aggregate pier with a larger diameter than itsoriginal cavity diameter.

Test Results:

FIG. 22 illustrates the results of testing of piers of the presentinvention as contrasted with a drilled concrete pier. The graphillustrates the movements of three aggregate piers constructed inaccordance with the invention (curves A, B, C) with a prior art drilledconcrete pier (curve D), as the piers are loaded with increasing loadsto maximum loads and then decreasing loads to zero load. The tests wereconducted using the following test conditions and using asteel-reinforced, drilled concrete pier as the control test pier.

A hole or cavity of approximately 8-inches in diameter was drilled to adepth of 20 feet and filled with concrete to form a drilled concretepier (test D). A steel reinforcing bar was placed in the center of thedrilled concrete pier to provide structural integrity. A cardboardcylindrical form 12 inches in diameter was placed in the upper portionof the pier to facilitate subsequent compressive load testing. Thematrix soil for all four tests was a fine to medium sand of mediumdensity with standard Penetration Blow Counts (SPT's) ranging from 3 to17 blows per foot. Groundwater was located at a depth of approximately10 feet below the ground surface.

The aggregate piers of the invention, reported as in tests A, B, and C,were made with a hollow tube 30, six (6) inches in external diameter andwith a special bottom head element 32 with an external diameter of 10inches. Tests A and B utilized aggregate only. Test C utilized aggregateand cementatious grout. Test A utilized predetermined lifting movementsof two feet and predetermined downward pushing movements of one footresulting in a plurality of one foot lifts. Test B utilizedpredetermined upward movements of three feet and predetermined downwardpushing movements of two feet, again resulting in one foot lifts. Test Cutilized predetermined upward movements of two feet and predetermineddownward pushing movements of one foot, and included addition ofcementatious grout.

Analyses of the data can be related to stiffness or modulus of the piersconstructed. At a deflection of 0.5 inches, test A corresponded to aload of 27 tons, test B corresponded to a load of 35 tons, test Ccorresponded to a load of 47 tons and test D corresponded to a load of16 tons. Thus at this amount of deflection (0.5 inches) and using test Bas the standard test and basis for comparison, ratios of relativestiffness for test B is 1.0, test A is 0.77, Test C is 1.34, and Test Dis 0.46. The standard, Test B, is 2.19 times stiffer than the controltest pier, Test D. The standard Test B is 1.30 times stiffer than TestA, whereas the Test C with grout additive is 2.94 times stiffer than theprior art concrete pier (Test D). This illustrates that the modulus ofthe piers formed by the invention are substantially superior to themodulus of the drilled, steel-reinforced concrete pier (Test D). Thesetests also illustrate that the process of three feet lifting movementwith two feet downward pushing movement was superior to the process oftwo feet lifting movement and one foot downward pushing movement. Thetests also illustrate that use of cementations grout additivesubstantially improved the stiffness of the formed pier for deflectionsless than about 0.75 inches, but did not substantially improve thestiffness of the formed pier compared with Test B for deflectionsgreater than about 0.9 inches.

In the embodiment disclosed, because the bulbous bottom head element 32of the hollow tube or hollow shaft 30 has a greater cross sectionalarea, various advantages result. First the configuration of theapparatus, when using a bottom valve mechanism 54, reduces the chancethat aggregate material will become clogged in the apparatus during theformation of the cavity 102 in the soil matrix 36 as well as when thehollow tube 30 is withdrawn partially from the soil matrix 36 to exposeor form a cavity 85 within the soil matrix 36. Further, theconfiguration allows additional energy from static force vectors anddynamic force vectors to be imparted through the bottom head element 32of the apparatus and impinge upon aggregate 44 in the cavity 70. Anotheradvantage is that the friction of the hollow tube 30 on the side of theformed cavity 102 in the ground is reduced due to the effective diameterof the hollow tube 30 being less than the effective diameter of thebottom head element 32 and therefore being less than the initialdiameter of the formed cavity. This permits quicker pushing into thesoil and allows pushing through formations that might be considered tobe more firm or rigid. The larger cross sectional area head element 32also enhances the ability to provide a cavity section 102 sized forreceipt of aggregate 44 which has a larger volume than would beassociated with the remainder of the hollow shaft 30 thus providing foradditional material for receipt of both longitudinal (or axial) andtransverse (or transaxial) forces when forming the lift 72. The reducedfriction of the hollow tube 30 on the side of the formed cavity 102 inthe soil 36 also provides the advantage of more easily raising thehollow tube 30 during pier formation and prevention of the hollow tube30 becoming stuck within the soil matrix.

In the process of the invention, the lowest lift 72 may be formed with alarger effective diameter and have a different amount of aggregateprovided therein. Thus the lower lift 72 or lowest lift in the pier 76may be configured to have a larger transverse cross section as well as agreater depth when forming a base for the pier 76. By way of example thelowest portion or lowest lift 72 may be created by lifting of the hollowshaft 30 four feet and then lowering the hollow tube 30 three feet, thusreducing the height of the lift 72 to one foot, whereas subsequent lifts72 may be created by raising the hollow shaft 30 three feet and thenlowering the hollow tube 30 two feet, thus reducing the thickness of thelift 72 to one foot.

The completed aggregate pier 76 may, as mentioned heretofore, bepreloaded after it has been formed by applying a static load or adynamic load 75 at the top of the pier 76 for a set period of time (seeFIG. 21). Thus a load 75 may be applied to the top of the aggregate pier76 for a period of time from 15 seconds to 15 minutes, or longer. Thisapplication of force may also provide a “modulus indicator test”inasmuch as a static load 75 applied to the top of the pier 76 can beaccompanied by measurement of the deflection accruing under the staticload 75. The modulus indicator test may be incorporated into the preloadof each pier to accomplish two purposes with one activity; namely, (1)applying a preload; and (2) performing a modulus indicator test.

The aggregate material 44 which is utilized in the making of the pier 76may be varied. That is, clean aggregate stone may be placed into acavity 85. Such stone may have a nominal size of 40 mm diameter withfewer than 5% having a nominal diameter of less than 2 mm. Subsequentlya grout may be introduced into the formed material as described above.The grout may be introduced simultaneous with the introduction of theaggregate 44 or prior or subsequent thereto.

When a vibration frequency is utilized to impart a dynamic force, thevibration frequency of the force imparted upon the hollow shaft orhollow tube 30 is preferably in a range between 300 and 3000 cycles perminute. The ratio of the various diameters of the hollow tube or shaft30 to the bulbous bottom head element 32 is typically in the range of0.92 to 0.50. As previously mentioned, the angle of the bottom bevel maytypically be between 30° and 60° relative to a longitudinal axis 35.

As a further feature of the invention, the method for forming a pier maybe performed by inserting the hollow tube 30 with the bulbous bottomhead element 32 to the total depth 81 of the intended pier.Subsequently, the hollow tube 30 and bulbous bottom head element 32 willbe raised the full length of the intended pier in a continuous motion asaggregate and/or grout or other liquid are being released or injectedinto the cavity as the hollow tube 30 and special bottom head element 32are lifted. Subsequently, upon reaching the top of the intended pier,the hollow tube 30 and special bottom head element 32 can again bestatically pushed and optionally augmented by vertically vibratingand/or ramming dynamic force mechanism downward toward or to the bottomof the pier in formation. The aggregate 44 and/or grout or othermaterial filling the cavity as previously discharged will be movedtransaxially into the soil matrix as it is displaced by the downwardlymoving hollow tube 30 and special bottom head element 32. The processmay then be repeated with the hollow tube 30 and special bottom headelement 32 raised either to the remaining length or depth of theintended pier or a lesser length in each instance with aggregate and/orliquid material filling in the newly created cavity as the hollow tube30 is lifted. In this manner, the material forming the pier may compriseone lift or a series of lifts with extra aggregate material and optionalgrout and/or other additives transferred laterally to the sides of thehollow cavity into the soil matrix. Alternatively, the last sequence canbe the same or similar to the “typical” aggregate pier forming method ofthis invention, whereas thin lifts are formed by raising and loweringthe hollow tube 30.

It is noted that the mechanism for implementing the aforesaid proceduresand methods may operate in an accelerated manner. Driving the hollowtube 30 and bulbous bottom head element 32 downwardly may be effectedrather quickly, for example, in a matter of two minutes or less. Raisingthe hollow tube 30 and bulbous bottom head element 32 incrementally apartial or full distance within the formed cavity may take even lesstime, depending upon the distance of the lifting movement and rate oflifting. Thus, the aggregate pier is formed from the soil matrix 36within a few minutes. The rate of production associated with themethodology and the apparatus of the invention is thereforesignificantly faster.

Additional Features:

FIGS. 27 through 36 illustrate additional features and embodiments ofthe invention. Referring to FIGS. 27, 27A and 27B, there is illustrateddiagrammatically, an apparatus including a hollow tube 500 coupled to abulbous bottom head element 502. The bulbous bottom head element 502includes central body 501 which is generally cylindrical with afrustoconical or conical shaped downwardly and inwardly inclined sectionor surface 504 surface joined to a generally horizontal section orsurface 505 with an opening 506 therethrough for passage of materialssuch as aggregate material, cementations material, grout or combinationsthereof. A separate horizontal plate 508 with generally verticallyextending rods 510 and 512 is positioned against closure cap 508 afitted against surface 505. The rods 510 and 512 fit along the outsideof the combination of hollow tube 500 and bottom head element 502. Theplate 508 may be in the form of a bar reinforced by angled plates 508Band 508C. Plate 508 engages circular cap or plate 503 which includesvertical pegs 511 that align plate 508 with opening 506 covering theopening 506 or in the form of a grid or other generally horizontalelement which is transported during placement of the hollow tube 500 andbulbous bottom head element 502 downwardly into the soil during theinitial penetration of the soil matrix. Then upon withdrawal of hollowtube 500 and head element 502, the plate 508 and rods 510 and 512 aswell as cap 503 will remain in place at the bottom end of the pier information. The rods, such as the rods 510 and 512, may, as shown in FIG.29, serve as an uplift anchor or as depicted in FIG. 30, may serve astell-tale rods for load testing. Thus, as depicted in FIGS. 29 and 30,the tell-tale rods 510 and 512 in combination with the lower connectingplate member 508 contemplate positioning of the described assembly onthe outside of the hollow tube 500 and bulbous bottom head element 502,yet are enabled to be positioned under the lower end of a formedaggregate pier such as pier 520 in FIG. 29 or pier 522 in FIG. 30.

FIG. 28 depicts a variation of the apparatus which may be utilized forthe practice of the invention. In this alternative apparatus, a hollowtube 526 is comprised of a series of connected or bolted tube sections528, 530 and 532, which extend longitudinally from an elevated hopper534 or they may extend longitudinally directly from the hollow tube. Thesmaller cross sectional portion of the hollow tube 526 is connected tothe bulbous bottom head element 536. In this manner, the overall weightof the hollow tube section can be reduced, yet the bulbous bottom headelement 536 will provide an adequate means and an adequate diameter forpenetration into a soil matrix. The hollow tube 526 will also provide anadequate channel for the passage of aggregate, crushed stone, roundedstone, crushed concrete, grout, cementatious material, or other pierforming materials, or combinations thereof.

Numerous variations of the multiple section hollow tube may bepracticed, although the typical sequence is for sections to decrease incross sectional area from top to bottom. Example variations includesections that increase in traverse cross sectional area toward the topend of the hollow tube. The sections may increase in traverse crosssectional area and then decrease. They may have the same traverse crosssectional area but distinct cross sectional configurations. They may beintegrally connected or detachable sections. Combinations of thesedescribed features may be used. The separate sections may bepre-assembled or they may be assembled seriatim at a work site as soilpenetration occurs. Typically, they are pre-assembled.

FIG. 31 illustrates a combination of features for use with a hollow tube540 and bulbous bottom head element 542 that facilitate alignment of thehollow tube 540 for soil penetration. Thus, a special alignment guidedevice 544 in the form of an annular support ring fits around the hollowtube 540 and is fastened to the drive mechanism. The alignment guidedevice 544 serves to guide the combination hollow tube 540 and bottomhead element 542 in the desired direction and location into a soilmatrix. The alignment guide or element 544 also prevents “kick out” ofthe hollow tube 540, especially when the matrix soil is hard or dense.One or more such alignment guide devices 544 may be utilized. The hollowtube 540 is generally slidably or moveably mounted within the guide 544.

FIG. 32 illustrates a feature that may be incorporated into the bulbousbottom head element 542, namely the placement of a sensor device 546within the bulbous bottom head element 542 for sensing the forcesimparted by the bulbous head or bottom head element 542 on the materialbeing discharged therefrom, as well as on the soil matrix. The forceapplied may be charted over time to provide a pattern of the effect ofthe bottom head element 542 upon compaction of the aggregate and uponpenetration of the soil matrix.

FIG. 33 illustrates a mechanism utilized to force the hollow tube 550and attached head element (not shown in FIG. 33) downwardly into a soilmatrix (not shown in FIG. 33). More specifically, the upper end 554 ofthe hollow tube 550 is fitted into a short cylindrical section 553 of aguide tube 555 welded to a connection tube 557, in turn, welded to asolid metal fitting 559 with a plate 552. The plate 552 is a horizontalplate and thus forces directed axially against that plate 252 willimpinge the plate 552 against the top end 554 of the hollow tube 550. Avibratory hammer 556 includes a mating plate 558 which may be fittedagainst the plate 552 and which is coupled thereto by means of rods orfasteners 561 projecting through the openings, such as opening 560, andlatches 562 to retain the plates 552 and 558 joined together. Thevibratory hammer 556 may then be operated to vibrate and drive thehollow tube 550 and head element (not shown) downwardly into the soilmatrix onto compact discharged aggregate, etc.

FIG. 34 illustrates a form or shape of a pre-penetration device whichmay be used in combination with a hollow tube apparatus and head elementas previously described. More particularly, a pre-penetration device maybe utilized to form a preliminary opening or passage within a soilmatrix, in particular, a stiff or medium dense soil. The device maycomprise a vertical rod 570 with a leading end 572 which is shaped orconfigured to facilitate soil penetration, such as having the shape of acone, for example. Generally, the large diameter end of the cone 572 isless than the maximum traverse dimension of a bulbous bottom headelement associated with a subsequent step in the process, namely thestep of using a bulbous bottom head element and hollow tube to penetrateinto the soil matrix. The shape and configuration of the penetrating end572, however, may be varied to accomplish the goal of providing a meansto facilitate the creation of an initial passage in the soil matrix intowhich a hollow tube and associated bulbous bottom head element willsubsequently be driven or inserted.

FIG. 35 illustrates another aspect of the method of the invention. Thatis, the method generally comprises use of a bulbous bottom head element,as described, and a hollow tube associated therewith to build a sectionor portion of an aggregate pier, such as a lower section 584, within asoil matrix 586. The region above the lower section 584 may subsequentlybe comprised of a pier construction, namely a pier construction 588,built in accord with some other teaching, for example the teaching asset forth in U.S. Pat. No. 5,249,892. The combination of pier sectionsof the type associated with the method of the present invention incombination with other pier forming methods is especially desirable oruseful, inasmuch as the technologies are compatible and will enable theconstruction of deeper piers in a highly efficient and extremely fastmanner inasmuch as the features associated with the respective sectionscompliment one another. For example, the upper pier portion formed byone teaching or method and apparatus may be of higher capacity than thelower pier portion associated with the method of the present invention.Stresses from loads are greater in the upper portion of a combined piersystem. Two, or more than two, types of pier constructions in verticalalignment are considered to be within the scope of the invention.

FIG. 36 is a diagrammatic view illustrating a typical bottom plan viewof a bulbous bottom head element made in accord with the invention. Aspreviously described, the bulbous bottom head element 600 is a bulbouselement and has a cross sectional dimension greater than that of thehollow tube element 602 attached adjacent thereto. The far distal end590 of the bulbous bottom head element typically includes an opening 592through which material such as aggregate or crushed stone, smooth stone,crushed concrete, grout, cementatious materials or the like, will flowduring the practice of the method. The bottom opening 592 is typically,as depicted in various figures, of a lesser dimension than thehorizontal face 590 at the extreme distal end 590 of the bulbous bottomhead element 600. The opening 592 thus, is typically less than one halfof the surface area of the traverse cross sectional area of the bottomhead element 600. Surface 590 with the opening 592, connects with ashaped surface 594 which generally is a conical shape. As previouslydescribed, however, other shapes may be used to provide a transitionfrom the outer surface 596 of the bulbous head element 600 to theextreme bottom surface 590 of the bulbous bottom head element 600.Moreover, the opening 592, as previously described, is initially coveredby a plate or a sacrificial cap or a closable cover, for example, duringinitial soil matrix penetration.

FIGS. 37 and 38 illustrate a further embodiment of the invention.Referring first to FIG. 37, there is disclosed a bulbous head element600 which is attached to a hollow pipe or mandrel 602. The hollow pipeor mandrel 602 includes a generally equal length second mandrel orhollow pipe of lesser diameter; namely, pipe 604 slidably positionedtherein. The hollow tubes or pipes 602 and 604 are joined together bybolts or pins 606 and 608 fitted through the upper end of the outerhollow tube 602 and the upper end of the interior hollow tube 604. Theinterior hollow tube 604 further includes at the lower end thereofpassages or openings 610 and 612 discussed with respect to FIG. 38.

Referring to FIG. 38 the interior mandrel or tube 604 may telescopelongitudinally in the direction of the longitudinal axis 616 upwardlyrelative to the lower mandrel or hollow tube 602 which is attached tothe bulbous head element 600. The pins or bolts 606 and 608 are removedfrom connecting the outer tube 602 to the inner tube 604 as depicted inFIG. 37 and then reinserted through the openings and in particular theopenings 610 and 612 to thereby elongate the effective operational limitor length of the hollow tube element which is comprised of thecombination of lengths of the lower and larger diameter hollow tube 602and the upper or lesser diameter hollow tube 604. A hopper or othermechanism may be provided for directing aggregate material into theinterior of the hollow tubes 602 and 604.

The embodiment of FIGS. 37 and 38 is especially useful in that itenables the practice of the methodology associated with the invention atdeeper depths within a soil matrix. That is, the soil matrix level isrepresented by the surface level 622 in FIG. 37. The combination of thebulbous head element 600 and the hollow tubes 602 and 604 may be placedin the soil matrix to the depth as illustrated in FIG. 37. Then,referring to FIG. 38, the tubes 602 and 604 may be telescoped and drivento a deeper depth. That is, the interior hollow tube 604 may be extendedas shown in FIG. 38 and the entire assembly then pushed down or placedfurther into the soil. In this manner, the combination of the bulboushead element 600 and the hollow tubes 602 and 604 may be inserted to amuch greater depth easily and quickly. The material fed through thehollow tube 602 and 604 may then be fed therein using the methodologiessuch as previously described. The telescoping tubes 602 and 604 enable asignificant increase of the depth which the methodology of the inventionmay be practiced in a very quick, efficient and economical manner. Ofcourse, all of the other features previously described may be used incombination with the telescoping mandrels or tubes described withrespect to FIGS. 37 and 38. Also, additional telescoping tubes may beutilized, although there may be a practical limit to such usage.Typically, the larger diameter tube 602 is attached to head element 600and positioned on the outside of the next telescoping tube 604 asillustrated in FIGS. 37 and 38, although the reverse may be adopted alsowith a larger diameter tube being on the outside of the smaller diametertube and the larger diameter tube being the tube which is raised orextended upwardly or telescoped away from the bulbous head element 600.

Various modifications and alterations may thus be made to themethodology as well as the apparatus to be within the scope of theinvention. Thus, it is possible to vary the construction and method ofoperation of the invention without departing from the spirit and scopethereof. Alternative hollow tube configurations, sizes, cross sectionalprofiles and lengths of tube may be utilized. The bulbous bottom headelement 32 may be varied in its configuration and use. The bottom valve54 may be varied in its configuration and use, or may be eliminated byadoption of a sacrificial cap. The leading end of the bulbous bottomhead element 32 may have any suitable shape. For example, it may bepointed, cone shaped, blunt, angled, screw shaped, or any shape thatwill facilitate penetration of a matrix soil and compaction ofdischarged aggregate material. The enlarged or bulbous bottom headelement 32 may be utilized in combination with one or more differingexternal diameter sections of the hollow tube 30 having various shapesor configurations. Therefore the invention is to be limited only by thefollowing claims and equivalents thereof.

1. A method for forming an aggregate pier in a matrix soil comprisingthe steps of: a) forming an elongate cavity having a bottom and alongitudinal axis in the matrix soil by lowering a hollow tube with abulbous bottom head element having an open end at the extreme endthereof including a closure mechanism for closing the extreme open end,said bulbous bottom head element configured with a greater crosssectional area portion than the cross sectional area of the adjacentconnected hollow tube and configured to provide axial and transaxialvector forces on the soil matrix, said closure mechanism closed duringformation of the elongate cavity to prevent aggregate material dischargefrom the bottom head element during formation of the cavity and toprevent clogging of the bottom head element or hollow tube with matrixsoil materials during penetration and formation of the elongate cavity;b) raising the hollow tube a predetermined first incremental distance inthe formed cavity; c) opening the closure mechanism when the hollow tubeis raised; d) feeding pier forming aggregate material through thespecial bottom head element extreme open end into the portion of thecavity revealed by raising the hollow tube said first incrementaldistance; and e) lowering the hollow tube a predetermined secondincremental distance to compact the discharged aggregate material in thecavity by axial and transaxial force impact from the bulbous bottom headelement onto the discharged aggregate material surface while displacinga portion of the pier forming aggregate material transaxially into thesidewalls of the filled cavity.
 2. The method of claim 1 wherein thehollow tube is initially forced a predetermined distance into the matrixsoil to form an elongate cavity.
 3. The method of claim 1 wherein theelongate cavity or a portion of its diameter is initially formed bypre-drilling or pre-penetrating the matrix soil to form an elongatecavity with diameter approximately the same as that of the bottom headelement or slightly less than that of the bottom head element and tosubsequently lower or partially lower and partially force, the hollowtube with bulbous bottom head element into the pre-formed elongatecavity.
 4. The method of claim 1 including the repetition of steps b)through e).
 5. The method of claim 1 including the step of closing theclosure mechanism before compacting.
 6. The method of claim 1 includingthe additional step of separately feeding a material in combination withthe aggregate material to facilitate aggregate flow and/or to increasethe strength and/or stiffness of the formed aggregate pier.
 7. Themethod of claim 1 wherein the step of compacting the dischargedaggregate comprises reducing the axial dimension of the compacted liftto about ½ to ¼ of the uncompacted aggregate incremental distance toform a compacted aggregate lift having a vertical axial dimension ofabout ½ to ¼ of the incremental distance the apparatus was raised duringstep (b).
 8. A method for forming an aggregate pier in a matrix soilcomprising the steps of: (a) forming an elongate cavity having a bottomand a longitudinal axis in a matrix soil by positioning a hollow tubewith a bulbous bottom head element into the matrix soil to apredetermined depth, said bottom head element having a bulbous shapewith a maximum cross sectional area greater than the attached hollowtube adjacent thereto, said bottom head element configured to impartaxial and transaxial forces on the matrix soil and on dischargedmaterials and having an extreme bottom end discharge opening with acover plate; (b) raising the hollow tube an incremental distance fromthe bottom of the cavity; (c) opening the bottom discharge opening andfeeding pier forming material through the hollow tube into the cavityupon raising of the hollow tube; and (d) vertically compacting the pierforming material with the head element by driving the hollow tube andhead element downwardly toward the bottom of the cavity while displacinga portion of the pier forming material transaxially in the cavity. 9.The method of claim 1 further including the step of forming a secondpier or pile segment of a type not formed by method of claim 1 upon anaggregate pier formed by the method of claim
 1. 10. The method of claim2 including the step of providing a static force on the hollow tube toeffect driving of the hollow tube and to effect compacting of dischargedaggregate.
 11. The method of claim 2 including the step of providing adynamic axial force and a static force on the hollow tube to effectdriving of the hollow tube and to effect compacting of dischargedaggregate.
 12. The method of claim 1 including the additional step ofpreloading the formed aggregate pier to increase its capacity andstrength.
 13. The method of claim 1 including the step of placing one ormore generally aligned rods with the hollow tube, said rod or rodsextending upwardly from a plate.
 14. The method of claim 1 wherein thefirst incremental distance is varied for at least one of therepetitions.
 15. The method of claim 1 wherein the first incrementaldistance is substantially equal to the height of the pier to be formed.16. Apparatus for construction of a soil reinforcement aggregate pier ina soil matrix comprising, in combination: an elongate hollow tube havinga longitudinal axis with a material entrance opening and a bulbousbottom head element having an open bottom discharge end, the externalcross section of the bulbous bottom head element being greater than theexternal cross section of the hollow tube adjacent thereto to therebyform a bulbous section of the hollow tube having an external crosssectional shape and size greater than the external cross sectional shapeand size of the hollow tube adjacent the bulbous end; said bulbous endhaving a surface configured to impart axial and transaxial forces upondownward movement on matrix soil and aggregate material; and saidbulbous end including a material discharge opening at the extreme endthereof with a removable cover plate or a valve that is able to open andclose.
 17. The apparatus of claim 16 wherein the hollow tube is furthercomprised of multiple sections each having a distinct cross sectionalarea.
 18. The apparatus of claim 16 further including at least two rodsmounted externally of the hollow tube and head element, said rodsattached to a plate external the hollow tube and head element.
 19. Theapparatus of claim 18 wherein the rods comprise uplift anchor rods aspart of an uplift anchor system.
 20. The apparatus of claim 18 whereinthe rods comprise tell-tale members.
 21. The apparatus of claim 16further including an alignment mechanism for stabilizing the hollow tubeand preventing it from laterally translating.
 22. The apparatus of claim16 further including a pressure detection sensor device mounted withinthe bulbous bottom head element to sense pressure.
 23. The apparatus ofclaim 16 in combination with a separate soil matrix pre-penetrationdevice to form a cavity prior to inserting the elongate hollow tube withbulbous bottom head element into the ground.
 24. The apparatus of claim16 further including a first plate mounted to the hollow tube and asecond plate attached to a vibratory hammer, said first and secondplates capable of being connected together by connecting rods and a lockmechanism.
 25. The apparatus of claim 16 wherein said hollow tube iscomprised of at least two telescoping longitudinal sections and one ofsaid sections is attached to said bottom head element.
 26. The apparatusof claim 25 including a releasable fastening mechanism for attaching thesections together in a non-telescoping configuration.
 27. The apparatusof claim 25 wherein said sections are concentric.
 28. The apparatus ofclaim 25 wherein the sections comprised a first larger diameter sectionattached to the head element and a second section slidably positionedwithin the first section.
 29. The apparatus of claim 25 including aradial pin removably connecting the sections.